Pesticides and old lace

November 4, 2017

The pesticide DDT is well-known for being one of the first targets of the environmentalist movement—attacked by Rachel Carson in her seminal book Silent Spring. But do you know what farmers used as pesticide before chemical advances such as DDT?

Arsenic.

That’s right, arsenic, or at least compounds of it such as lead arsenate and calcium arsenate, was the first insecticide. As described by Stephen Yafa in his history of cotton:

The poison arrived in two popular compounds, calcium arsenate and highly toxic copper acetoarsenite, commonly known as Paris green. Farmers applied three million pounds of those powders in that year [1919]. “I carried poison to the cotton fields maybe four or five rows and… shake that sack over the cotton and when I’d look back, heap of times… that cotton would be white with dust, behind me,” [farmer Nate] Shaw recalled late in life, “and I’d wear a mask over my mouth—still that poison would get in my lungs and bother me.”

Arsenic is potent, and caused lots of problems:

As a youngster [farmer Marshall] Grant was given the job of pulling a mule duster to apply calcium arsenate over infested plants. He soon learned to wear long pants to protect his skin against the stinging powder. He also took showers day and night. The papers were full of stories about children on farms forgetting to wash up, becoming violently ill from the dust, and occasionally dying. Rains carried the insecticide into nearby streams. After a few years, most of the rabbits and small game that Grant (and Shaw, in Alabama) loved to hunt began to disappear.

Arsenic left over in the soil from the early 20th century is still a problem today for some crops.

In this context, it’s easy to see how synthetic insecticides were a major advance:

They came out of wartime experiments and killed a wide variety of insects on contact, while arsenic had to be ingested. In 1939 a Swiss chemist, Paul Müller, discovered that an organic chlorine originally synthesized in the nineteenth century killed insects with remarkable efficiency. That poison with an unpronounceable name quickly became known by its initials, DDT. From the moment of its appearance, DDT was hailed as the twentieth century’s miracle disease-eradicator, and by 1943 it was solely responsible for keeping thousands of GIs alive. By then, more American soldiers were dying from insect-borne diseases in the tropical Pacific than from combat. As many as 50 million civilians had died from malaria and typhus during the previous decade. DDT powder quickly began to reverse that carnage by eliminating the insects responsible, along with houseflies, bedbugs, fleas, hornflies, and lice.